The ICR said that testing for those genes could be used to target prevention efforts on women most at risk of developing disease and to test new treatments.

Baroness Morgan of Drefelin, the chief executive at Breast Cancer Now, which funded the study, said: “These are really important findings. We urgently need to unravel how the genetic changes in the building blocks of our DNA influence a woman’s risk of breast cancer, and this study adds another vital piece to this jigsaw.

“More women are now being diagnosed with breast cancer than ever before, and these crucial findings could ultimately help us more accurately predict who is most at risk and develop new targeted treatments.”

Dr Olivia Fletcher, team leader in functional genetic epidemiology at the institute, said: “Identifying these new genes will help us to understand in much greater detail the genetics of breast cancer risk. Ultimately, our study could pave the way for new genetic tests to predict a woman’s risk, or new types of targeted treatment.”

Professor Paul Workman, the chief executive of the ICR, said: “Large-scale genomic studies have been instrumental in associating areas of our DNA with an increased risk of breast cancer. This study brings these regions of DNA into sharper focus, uncovering a treasure trove of genes that can now be investigated in more detail.”